>> RELATED: 5 dead in mass shooting near Pittsburgh

1. The shooting occurred at a backyard party/cookout. At least two gunmen opened fire in an ambush-style attack at the Franklin Avenue home, according to authorities. Police said the ballistic evidence at the scene leads investigators to believe that two different weapons were discharged by two different people. Shots were fired from an alley to the rear of the home.

Police said partygoers appeared to try to run into the home, at which point a person on the side or in the backyard adjacent to the house fired at the back porch.

5. A witness said at least 20 shots were fired. A witness told WPXI that she was walking home when she heard the shots and saw people running from the area. She said authorities kept her from getting to her home on Franklin Avenue, which she described as a quiet street.